Return-Path: Received: from smtp-out.google.com ([216.239.44.51]:15710 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932301Ab0EXXqe (ORCPT ); Mon, 24 May 2010 19:46:34 -0400 Date: Mon, 24 May 2010 16:46:24 -0700 (PDT) From: Hugh Dickins To: Greg KH cc: Alan Cox , Tharindu Rukshan Bamunuarachchi , linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: TMPFS over NFSv4 In-Reply-To: <20100524110903.72524853@lxorguk.ukuu.org.uk> Message-ID: References: <20100524110903.72524853@lxorguk.ukuu.org.uk> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Hi Greg, On Mon, 24 May 2010, Alan Cox wrote: > On Mon, 24 May 2010 02:57:30 -0700 > Hugh Dickins wrote: > > On Mon, May 24, 2010 at 2:26 AM, Tharindu Rukshan Bamunuarachchi > > wrote: > > > thankx a lot Hugh ... I will try this out ... (bit harder patch > > > already patched SLES kernel :-p ) .... > > > > If patch conflicts are a problem, you really only need to put in the > > two-liner patch to mm/mmap.c: Alan was seeking perfection in > > the rest of the patch, but you can get away without it. > > > > > > > > BTW, what does Alan means by "strict overcommit" ? > > > > Ah, that phrase, yes, it's a nonsense, but many of us do say it by mistake. > > Alan meant to say "strict no-overcommit". > > No I always meant to say 'strict overcommit'. It avoids excess negatives > and "no noovercommit" discussions. > > I guess 'strict overcommit control' would have been clearer 8) > > Alan I see we've just missed 2.6.27.47-rc1, but if there's to be an -rc2, please include Alan's 2.6.28 oops fix below: which Tharindu appears to be needing - just now discussed on linux-mm and linux-nfs. Failing that, please queue it up for 2.6.27.48. Or if you'd prefer a smaller patch for -stable, then just the mm/mmap.c part of it should suffice: I think it's fair to say that the rest of the patch was more precautionary - as Alan describes, for catching other bugs, so good for an ongoing development tree, but not necessarily in -stable. (However, Alan may disagree - I've already misrepresented him once here!) Thanks, Hugh commit 731572d39fcd3498702eda4600db4c43d51e0b26 Author: Alan Cox Date: Wed Oct 29 14:01:20 2008 -0700 nfsd: fix vm overcommit crash Junjiro R. Okajima reported a problem where knfsd crashes if you are using it to export shmemfs objects and run strict overcommit. In this situation the current->mm based modifier to the overcommit goes through a NULL pointer. We could simply check for NULL and skip the modifier but we've caught other real bugs in the past from mm being NULL here - cases where we did need a valid mm set up (eg the exec bug about a year ago). To preserve the checks and get the logic we want shuffle the checking around and add a new helper to the vm_ security wrappers Also fix a current->mm reference in nommu that should use the passed mm [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix build] Reported-by: Junjiro R. Okajima Acked-by: James Morris Signed-off-by: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds diff --git a/include/linux/security.h b/include/linux/security.h index f5c4a51..c13f1ce 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1585,6 +1585,7 @@ int security_syslog(int type); int security_settime(struct timespec *ts, struct timezone *tz); int security_vm_enough_memory(long pages); int security_vm_enough_memory_mm(struct mm_struct *mm, long pages); +int security_vm_enough_memory_kern(long pages); int security_bprm_alloc(struct linux_binprm *bprm); void security_bprm_free(struct linux_binprm *bprm); void security_bprm_apply_creds(struct linux_binprm *bprm, int unsafe); @@ -1820,6 +1821,11 @@ static inline int security_vm_enough_memory(long pages) return cap_vm_enough_memory(current->mm, pages); } +static inline int security_vm_enough_memory_kern(long pages) +{ + return cap_vm_enough_memory(current->mm, pages); +} + static inline int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) { return cap_vm_enough_memory(mm, pages); diff --git a/mm/mmap.c b/mm/mmap.c index 74f4d15..de14ac2 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -175,7 +175,8 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) /* Don't let a single process grow too big: leave 3% of the size of this process for other processes */ - allowed -= mm->total_vm / 32; + if (mm) + allowed -= mm->total_vm / 32; /* * cast `allowed' as a signed long because vm_committed_space diff --git a/mm/nommu.c b/mm/nommu.c index 2696b24..7695dc8 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1454,7 +1454,8 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) /* Don't let a single process grow too big: leave 3% of the size of this process for other processes */ - allowed -= current->mm->total_vm / 32; + if (mm) + allowed -= mm->total_vm / 32; /* * cast `allowed' as a signed long because vm_committed_space diff --git a/mm/shmem.c b/mm/shmem.c index d38d7e6..0ed0752 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -161,8 +161,8 @@ static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb) */ static inline int shmem_acct_size(unsigned long flags, loff_t size) { - return (flags & VM_ACCOUNT)? - security_vm_enough_memory(VM_ACCT(size)): 0; + return (flags & VM_ACCOUNT) ? + security_vm_enough_memory_kern(VM_ACCT(size)) : 0; } static inline void shmem_unacct_size(unsigned long flags, loff_t size) @@ -179,8 +179,8 @@ static inline void shmem_unacct_size(unsigned long flags, loff_t size) */ static inline int shmem_acct_block(unsigned long flags) { - return (flags & VM_ACCOUNT)? - 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE)); + return (flags & VM_ACCOUNT) ? + 0 : security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)); } static inline void shmem_unacct_blocks(unsigned long flags, long pages) diff --git a/security/security.c b/security/security.c index 255b085..c0acfa7 100644 --- a/security/security.c +++ b/security/security.c @@ -198,14 +198,23 @@ int security_settime(struct timespec *ts, struct timezone *tz) int security_vm_enough_memory(long pages) { + WARN_ON(current->mm == NULL); return security_ops->vm_enough_memory(current->mm, pages); } int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) { + WARN_ON(mm == NULL); return security_ops->vm_enough_memory(mm, pages); } +int security_vm_enough_memory_kern(long pages) +{ + /* If current->mm is a kernel thread then we will pass NULL, + for this specific case that is fine */ + return security_ops->vm_enough_memory(current->mm, pages); +} + int security_bprm_alloc(struct linux_binprm *bprm) { return security_ops->bprm_alloc_security(bprm);